Parkinson's disease (PD) is the most common neurodegenerative disorder of the basal ganglia. Although many effective treatments for the motor symptoms of PD exist, their benefits are limited in degree and duration. The greatest challenge posed by this disease is to develop therapies that address the underlying degenerative process. The overriding theme of the Udall Center at Columbia is to address this challenge. Our efforts have two guiding principles. The first is that development of such therapies ultimately depends on a better understanding of mechanisms of disease. The second is that patients cannot wait for a full understanding of this disease to be in hand before efforts are made to translate new knowledge into treatments. Based on these principles, our proposal consists of four Projects that will be integrated according to five current central themes in the pathogenesis of PD. Each of the Projects builds on discoveries in the genetics of PD. Project 1 (Sulzer &Cuervo) will continue their important work on the degradation of a-synuclein. Projects 2 (Dauer) and 3 (Greene) will explore, in collaboration, mechanisms of LRRK2 toxicity. Project 4 (Burke) will utilize a new hl_RRK2(R1441G) BAG transgenic model of PD, in which he has identified a dopaminergic axonopathy, in translational investigations. This model will be available to Projects 2 and 3. Project 1 will also examine relationships between processing of synuclein and two important components of the intracellular milieu of dopamine neurons: cytosolic dopamine and calcium. One of the central themes of our Udall Center has been to examine the role of programmed cell death in pathogenesis. This theme has taken on a new importance due to the work of Dr Dauer in Project 3, demonstrating an interaction of LRRK2 with proteins in the extrinsic cell death pathway. Independent lines of investigation in Projects 3 (Greene) and 4 (Burke) have converged on the importance of the survival signaling kinase Akt in the viability of dopamine neurons. The importance of chaperone-mediated autophagy in degradation of synuclein has been discovered in the current funding period in Project 1, and the role of macroautophagy in the maintenance of axons has emerged in Project 4. To support the emphasis in the current proposal on the translational implications of our work, the Center now includes a Brain Bank Core, a Core for Training in Translational Neuroscience, and a Fibroblast Core for the production of human pluripotent cells. Thus the Udall Center at Columbia is poised to discover new approaches to neuroprotection and restoration, and to move these discoveries to the clinic expeditiously. Public Health Relevance: Current therapies for PD treat only its symptoms, not its progression. The goal of our research is to use new knowledge about the mechanisms of neurodegeneration to develop therapies that will block progression. We use genetic and neurotoxin models to better understand these mechanisms. We realize that patients cannot wait for us to understand mechanisms completely before we try to develop new therapies. Therefore, we will also go forward with translational research to establish novel pharmacologic and gene therapies. PROJECT 1 Principal Investigator: David Sulzer, Ph.D. Title: Roles for Alpha-Synuclein Degradation and Cytosolic Dopamine in Pd Pathogenesis Description (provided by applicant): We will extend a line of investigation that suggests that "multiple hits", consisting of mishandling of 1) alphasynuclein (a-syn) degradation, 2) cytosolic calcium, and 3) cytosolic dopamine (DA), underlie Parkinson's disease (PD). Our preliminary results indicate that if any of these factors are absent in neuronal culture models of selective substantia nigra (SN) death, neurodegeneration can be blocked. During the prior Udall period, we 1) developed intracellular patch electrochemistry (IPE) to measure cytosolic dopamine (Mosharov et al., 2003;Mosharov et al., 2006b) and 2) reported that a-syn is specifically degraded within specialized lysosomes by chaperone-mediated autophagy (CMA), but that pathogenic a-syn mutants and DA-modified-a-syn (DA-syn) block CMA (Cuervo et al., 2004;Martinez-Vicente et al., 2008). In the current proposal, we characterize how a-syn is trafficked to lysosomes and blocks CMA (Aim 1) how cytosolic Ca++ controls cytosolic DA in SN neurons (Aim 2) and how the combination of these three "hits" disturbs normal homeostasis and may cause in pathology in mice (Aim 3). Public Health Relevance: This research is designed to test a hypothesis that may explain the "root cause" of many cases of Parkinson's Disease, the second most common neurodegenerative disorder.